Scripture is not so forth coming to be understood on one's own. The only way to conclude that Jesus was the pierced one of Zechariah 12:10 is to acknowledge the high 'christology' of John's Gospel.
They look on him…thrust through: another possible rendering is “they shall look to me concerning him…thrust through.” In either case, the victim is an enigmatic figure, perhaps referring to a Davidic descendant, a priestly leader, or even a true prophet. Some historical event, unknown to us from any surviving source, may underlie this reference. The Gospel of John applies this text to the piercing of Christ’s side after his death.
The mourning for the pierced victim in Jerusalem is compared to the annual ritual mourning in the plain of Megiddo over the death of the Phoenician fertility god, Hadadrimmon. According to others, Hadadrimmon is the name of a place near Megiddo, and the reference would then be to the mourning over the death of King Josiah at the hands of Pharaoh Neco in 609 B.C. i'm sure there are objections to this interpretation as well.